Does Ashton Kutcher want to have a baby with his wife Demi Moore? Ashton discusses the possibility of daddyhood and dishes secrets about Demi's fab figure on tonight's "Nightline."

Ashton, who's helped raise Demi and Bruce Willis' three daughters, tells "Nightline" co-anchor Cynthia McFadden that he doesn't know whether or not he and Demi will eventually welcome a child of their own.

"There's something awfully attractive about having our third girl [Demi and Bruce's youngest daughter, Tallulah Belle] -- she's 16 now, she's gaining some independence," Ashton says. "There's a level of independence that we've never had in our relationship… and an ability to just spend time together doing things, that I think that we might want to take advantage of."

When McFadden suggests that gorgeous 47-year-old Demi might be running out of time to have a biological child, Ashton, 32, says: "I think my wife is a genetic freak."

Catch Ashton's full interview tonight at 11:35 p.m. on ABC's "Nightline."

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